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Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img conve
From: |
Dmitry Konishchev |
Subject: |
Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated() |
Date: |
Wed, 15 Jun 2011 17:14:47 +0400 |
On Wed, Jun 15, 2011 at 4:02 PM, Stefan Hajnoczi <address@hidden> wrote:
> We need to fully understand performance before applying optimizations
> on top. Otherwise it is possible to paper over a problem while
> leaving the root cause unsolved. Avoiding lseek(2) is very important,
> not just for qemu-img but also for running VMs. lseek(2) should only
> be invoked if the image is growable/removable.
>
> When I run a VM from a virtio-blk raw image I see no lseek(2) calls.
>
> On the host:
> strace -p $pid_of_qemu -f
>
> Inside the guest:
> dd if=/dev/vda of=/dev/null iflag=direct
>
> I see pread(2) from the posix-aio-compat.c worker threads but no
> lseek(2). The total_sectors cached value is being used.
>
> Does strace(1) show lseek(2) on your host?
No, I don't see lseek() in the strace output. But in the other hand I
see that bdrv_get_geometry() uses bdrv_getlength() which is
implemented using lseek() in block/raw-posix.c...
May be I'am mistaken about lseek(), but I get 9% slower version if
disable caching.
--
Дмитрий Конищев (Dmitry Konishchev)
mailto:address@hidden
- [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/08
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/13
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/13
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/14
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/14
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(),
Dmitry Konishchev <=
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/16
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/17
[Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15